Conventionally, various treating methods are performed on various kinds of food including fruits or vegetables. More specifically, (1) to soften the texture of food, food such as vegetables is heated, (2) to extract a liquid component such as juice, food such as fruits is cut into pieces, (3) to make pickles, food is dehydrated through the use of the osmotic effect of salt to allow seasonings to penetrate the food, and (4) to make powdered green tea, tea leaves are ground into powder. In the case where a liquid component is extracted from very hard food such as sugarcane, after the food is cut into pieces as described above, the pieces of food may be compressed with extremely high pressure.
As the method of treating food, various techniques have been already proposed. More specifically, to easily impregnate food with a liquid or a gas in a short time, a technique of bringing the liquid or the gas into contact with the food in a reduced pressure environment, or a technique of bringing the liquid or the gas in contact with food subjected to decompression treatment is known (for example, refer to Patent Literature 1).    [Patent Literature 1] Japanese Unexamined Patent Application Publication No. 2003-174850